1. Field of the Invention
The invention relates to a pump, in particular a piston pump, having a valve through which a fluid can selectively flow and which has a receptacle for movably guiding a spherical blocking body and has a valve seat adapted three-dimensionally to the spherical shape of the blocking body.
2. Description of the Prior Art
Piston pumps are used, among other purposes, in known vehicle brake systems, especially anti-lock brake systems (ABS). There, they serve to control the pressure in wheel brake cylinders. In the ABS, they are provided for instance for returning brake fluid from one or more wheel brake cylinders to a master cylinder. Often, the ABS functions in combination with traction control (TC), which likewise makes use of piston pumps. A further known system, known as an electronic stability program (ESP), improves the driving safety by a further increment over ABS and TC by varying the crosswise dynamics of the vehicle. In this system as well, piston pumps are employed.
Known pumps used particularly for vehicle brake systems have valves, for controlling the fluid flow direction through the pump, which are as a rule embodied as check valves acted upon springs and serve as inlet and outlet valves. Preferably, the check valves acted upon by springs are embodied in the form of ball-seat valves, including a blocking body in the form of a ball and a valve seat adapted three-dimensionally to the spherical shape of the blocking body. In the case of the ball-seat valves acting as an outlet valve, the ball is usually guided in a receptacle embodied in an outlet valve cap of the known piston pumps. When fluid flows out through an outflow bore embodied in the piston pumps, the ball opens the outlet region in accordance with the following principle. The ball migrates tangentially out of the sealing seat in the direction of the outlet valve cap bottom and the outflow bore. The ball in this case opens only minimally, since a dynamic pressure develops upstream of the ball. In addition, the ball is drawn into the outflow groove, directly adjoining the valve seat, by the outflow of the fluid. Overall, in the pump interior of known piston pumps, a high dynamic pressure develops, which results in high stress on components. Moreover, because of what is described above, known piston pumps have high driving torque and accordingly a high system output.